The present invention relates to a sheet feeding device used for an image forming apparatus such as a copier, a printer, a facsimile, and a multi-functional machine having the functions thereof and more particularly to a sheet feeding device having a cleaning member for removing foreign substances such as paper dust adhered to the outer peripheral surface of a conveying member and an image forming apparatus having the sheet feeding device.
Conventionally, a foreign substance removing device of the image forming apparatus makes a fixing type cleaning member (a flexible member such as a brush, felt, or a PET sheet) touch a roller member for conveying recording sheets, thereby removes foreign substances such as paper dust. Further, it makes a cleaning roller (a brush, felt, etc.) touch conveyed recording sheets, thereby removes foreign substances such as paper dust.
For example, Unexamined Japanese Patent Application Publication No. 11-52641 discloses a foreign substance removing device for making a fixed type cleaning member such as felt touch a conveying roller, thereby cleaning the surface of each recording sheet by the conveying roller.
Unexamined Japanese Patent Application Publication No. 11-208918 makes a brush touch a cleaning roller for cleaning conveyed recording sheets, thereby cleans the cleaning roller.
Unexamined Japanese Patent Application Publication No. 08-314344 is of a type of making a cleaning roller touch conveyed recording sheets.
Unexamined Japanese Patent Application Publication No. 2004-224451 makes a rotating brush roller touch a conveying roller, thereby cleans the conveying roller, makes a rotary roller touch the brush roller, thereby cleans the brush roller, and furthermore makes a flexible sheet touch the brush roller, thereby cleans the rotary roller.
Unexamined Japanese Patent Application Publication No. 2004-137076 (paragraph 0101, FIG. 9(a)), in a case that a conveying roller and a foreign substance removing member are rotated in the opposite direction and a case that they are rotated in the same direction, provides a speed difference between the moving speed of the tip of the foreign substance removing member and the moving speed of the peripheral surface of the conveying roller.
When feeding recorded sheets, particularly offset-printed sheets to the sheet feeding device arranged in the image forming apparatus or finisher, dusting powder or ink sludge adhered to a sheet and a coating agent on the sheet surface are adhered to the outer peripheral surfaces of the feed roller and conveying roller, thus the conveying force of the feed roller and conveying roller is lowered, and the sheet conveying performance becomes unstable. Therefore, it is necessary to clean the conveying roller.
However, in the foreign substance removing device for making a fixing type cleaning member touch the aforementioned feed roller and conveying roller, thereby removing foreign substances or making a cleaning roller such as a rotating brush touch a conveyed transfer material, thereby removing foreign substances and in the image forming apparatus using it, foreign substances such as paper dust cannot be stably removed over a long period of time, thus a problem arises that entering of foreign substances into the transfer area cannot be reduced for a long time.
Further, in the feed roller system of a reverse roller type, foreign substance stains such as paper dust adhered to the rotary rollers such as the pickup roller and feed roller are cleaned by pressing a flexible member such as a raising member like moquette, foamed polyurethane, or a PET sheet to the rollers. However, the raising member and flexible member cannot separate scraped foreign substances from the rollers, so that the cleaning effect is not continued, and it is necessary to periodically clean or exchange the cleaning member and rollers.
In the image forming apparatus disclosed in Unexamined Japanese Patent Application Publication No. 11-52641, foreign substances such as paper dust are collected immediately in the cleaning member, and unremovable foreign substances such as paper dust are conveyed into the transfer area, thus there is a problem imposed in the durability.
In the image forming apparatus disclosed in Unexamined Japanese Patent Application Publication No. 11-208918, a speed difference is provided between the cleaning roller and the transfer material, so that a problem arises that an unstable element is given to conveyance of the transfer material.
In the image forming apparatus disclosed in Unexamined Japanese Patent Application Publication No. 08-314344, at the point of time when foreign substances such as paper dust are collected on the surface of the cleaning roller, the effect is lost and there is a problem imposed in the durability.
In the image forming apparatus disclosed in Unexamined Japanese Patent Application Publication No. 2004-224451, unless the rubber of the conveying roller and the material of the cleaning member are set appropriately, stable sheet conveyability and a high effect cannot be obtained.
In the foreign substance removing apparatus disclosed in Unexamined Japanese Patent Application Publication No. 2004-137076, when the conveying roller and brush of the foreign substance removing member are rotated in the opposite direction, it is described to make the brush touch the peripheral surface of the conveying roller so as to move relatively. However, the relationship between the moving speed of the sliding section of the front end of the brush and the moving speed of the outer peripheral surface of the conveying roller is not described.
Further, the pickup roller of the sheet feeding device must send surely sheets to the feed roller and the pressurizing force of the pickup roller to sheets must be set to an appropriate load. To give a stable and appropriate load, a system of applying pressurizing force by the own weights of the pickup roller and holder is effective. However, in this case, when the cleaning mechanism for cleaning the pickup roller is made larger, a problem arises that an appropriate load cannot be given.